The overall objective is to determine the extent to which intratumoral macrophages in regressing and progressing tumors are activated for tumor cell killing. Monoclonal antibodies will be produced as a means of attaining this objective. The rationale behind the research is that activators cause the expression of new components within and on the surface of macrophages. Antigenic determinants on some of these components should be sufficiently specific to constitute markers for the individual stages that lead to the fully activated, cytolytic state. Our preliminary results, as well as those from other laboratories, support the validity of this hypothesis. We will accomplish our objective by attaining the following specific aims: (i) Identify rat monoclonal antibodies that will detect marker phenotypes that are specific for individual stages of mouse macraphage activation. Immunization with isolated proteins that have been associated with activation stages by 2-dimensional electrophoretic analysis will be the primary approach. For selected purposes immunization with intact macrophages that have been treated to be in a given stage of activation may also be needed. (ii) Use the stage phenotypes to monitor the development and loss of activation stages in vitro (macrophages cultured from bone marrow) and in vivo, in regressing and progressing Moloney sarcomas. (iii) Determine the effects of an immunomodulator on the state of macrophage activation in progressively growing tumors. Various agents, such as recombinant gamma interferon, will be injected either intratumorally or systemically until an efficacious immunomodulator is identified, i.e., one that has a distinct anti-tumor effect. If needed to produce an anti-tumor effect, the soluble immunomodulator will be incorporated in liposomes before injecting it. The proposed research is important because it will allow intralesional analysis of the state of macrophage activation for the first time. It is expected that the approach will be equally applicable to the analysis of macrophages in granulomas and other inflammatory responses against infectious agents, a fact that increases the importance that the technology will potentially have.